A basic question in the proposed research is what factors differentiate male alcoholics from their nonalcoholic male siblings. Past research on the genetics of alcoholism has demonstrated that direct genetic influences can be a factor for only a minority of diagnosed alcoholics; therefore, environmental influences must play an important role. Two sources of environment have been identified as important to development in general. First is the shared or common environment that siblings experience while growing up in the same home, such as similar child rearing practices provided by the parents. Second are environmental influences that are unique to each individual in the family such as different peer groups and different developmental histories. Results of recent twin and adoption studies indicate that the nonshared type plays a far greater role in personality development than does shared environment. This study will investigate the impact of both these environmental factors on the development of alcoholism. In addition, we will also investigate the role of personality factors and individual coping strategies, since there is suggestive evidence both may buffer or exacerbate a predisposition to alcohol disorders. We will recruit 100 pairs of siblings; one member of each pair will meet criteria for an alcohol disorder diagnosis and the other member will be free of alcohol and drug problems. Half of the pairs will have an alcoholic father and half will have no first or second degree family history of alcoholism. Subjects will be administered an extensive battery of instruments that will assess personality, both shared and nonshared environment, and coping strategies. Thus, this study will be able to investigate the conjoint effects of family history, environment, and personality on the development of alcoholism. The results of this research could have important implications for early intervention efforts, especially for individuals at a putative genetic risk for alcoholism. The information obtained should provide a frame of reference for tailoring treatment programs to specific developmental histories. The study results should also provide important new information on the role of environmental factors in the etiology of alcoholism